Portable computing devices—such as laptop computers, notebook computers, tablet style computers, hand-held computing devices (e.g., a personal digital assistant, or PDA), and the like—have become nearly ubiquitous as their desktop relatives. Users of portable computers often need access to a computer network yet, due to their mobility, a user of such a portable device may not have access to a wired network connection. Thus, the ability to access a network via a wireless network connection, or otherwise to conduct wireless communications, is highly desirable for these mobile computing devices.
Mobile computer users may need to conduct wireless networking activities in a variety of network environments at different times or even simultaneously. By way of example, a user may wish to communicate wirelessly over a relatively short range with a network or with individual devices (e.g., printers and other peripherals). A network—or, more generally, a wireless connection between two or more devices—that takes place over a relatively short range (e.g., up to 10 meters) is sometimes referred to as a Personal Area Network, or PAN. The user may also need to establish a wireless connection with a Local Area Network, or LAN. A typical wireless LAN connection may extend over a range of, for example, from 10 to 100 meters. Further, the user of this mobile computing device may want to establish a wireless connection with a network over a relatively long range (e.g., greater than 100 meters). A network extending over a vast region is often referred to as a Wide Area Network, or WAN.
One technology used for establishing wireless PAN connections is Bluetooth™. Bluetooth is a short range, low power radio technology that supports both voice and data applications, and this technology provides frequency-hopping spread spectrum (FHSS) radio connections over multiple channels in the 2.4 GHz radio band (more precisely, in the 2.4 to 2.4835 GHz band). Bluetooth wireless technology generally supports a range up to 10 meters, although longer distances are possible with more powerful radios.
A wireless LAN technology is defined in the IEEE (Institute of Electrical and Electronics Engineers) 802.11 family of specifications, including 802.11a and 802.11b. The IEEE 802.11b standard defines wireless services over a 2.4 GHz band that spans a frequency range of 2.4 to 2.4835 GHz, whereas IEEE 802.11a defines wireless services over a number of bands in the 5 GHz frequency range, including 5.15 to 5.25 GHz, 5.25 to 5.35 GHz, and 5.725 to 5.825 GHz.
A technology useful for wireless WAN communications is the General Packet Radio Service, or GPRS. GPRS provides wireless, packet-based services over a GSM™ (Global System for Mobile Communications) network. A GSM network can be implemented in any frequency band; however, there are several frequency bands that are currently (or will shortly be) in use, including GSM400 (450.4–457.6 MHz and 460.4–467.6 MHz or 478.8–486 MHz and 488.8–496 MHz), GSM850 (824–849 MHz and 869–894 MHz), GSM900 (880–915 MHz and 925–960 MHz), GSM1800 (1710–1785 MHz and 1805–1880 MHz), and GSM1900 (1850–1910 MHz and 1930–1990 MHz).
Despite the availability of the above-described technologies, as well as others, to conduct wireless network communications at various frequencies, in a number of environments (e.g., a PAN, LAN, or WAN), and over various distances, a typical portable computing device is equipped or configured to operate in only one wireless RF (radio frequency) communications mode. A number of parameters may characterize a particular RF communications mode, including frequency, range or distance, networking environment (e.g., PAN, LAN, or WAN), and the communications standard or technology (e.g., Bluetooth, IEEE 802.11a and 802.11b, GPRS, etc.). A wireless RF communication mode will be referred to herein as simply a “mode.”
A single mode computing device generally has one antenna optimized for that communication mode. For example, a portable computer may have a single antenna that is designed for wireless Bluetooth services in the 2.4 GHz band and, further, that is optimized for use over a relatively short range. However, this antenna may function poorly in other modes (e.g., in IEEE 802.11a or in a GPRS mode).
A variety of peripheral cards (e.g., PC Cards, PCI cards, etc.) providing wireless networking capabilities are presently available, and it may be possible to adapt a portable computer for use in multiple modes (e.g., for both Bluetooth in the 2.4 GHz band and IEEE 802.11a in the 5 GHz band). However, adapting a portable computing device for wireless networking in multiple modes using add-on peripheral cards may be impeded by space constraints, as space is generally at a premium in portable computers. Further, the placement of multiple antennas—each for use with a different mode—on a portable computing device presents co-existence problems, as a lack of isolation between antennas may lead to interference and cross-talk.